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M A S T E R P A N E L
page 3 – 31
E-6 / Dec 2007
DEPTH (0.0dB - 40.0dB) — The maximum amount the expander is permit-
ted to reduce the input signal level.
OPEN (1.00mS - 100.0mS) — The time-constant of the rate at which the
expander un-attenuates, or opens; sometimes called “attack”.
HANG (0.00mS - 1.000S) — An adjustable period of time the expander
remains open without attenuating, before starting to close. Handy to keep the
expander open during, say, speech inter-syllables or other short pauses, without
having to resort to excessively long...
CLOSE (50.0mS - 3.000S) — ... close times, being the rate at which the
expander attenuates away the input signal once below the threshold.
A graphical input/output plot at the top of the Dynamics screen shows the
combined effects of the compressor and expander on the signal.
Almost always, the trick is to set the threshold of the expander - below which
it starts to attenuate away the input signal - high enough to capture the noise, but
not too high as to snatch at the lower levels of the desired parts of the program
material. That can sound really irritating.
Sometimes the gain reduction is required to be subtle so as not to draw
attention to the fact that the expander is in operation; under these conditions
shallow expansion ratios, such as 1:1.5 or 1:2 are preferred, as are restricted
depth - 6dB, or 10dB, is plenty and makes a substantial subjective improvement
to the noise.
These, too, are the kind of settings used for another application of an
expander: effectively shortening an excessively long room reverberation time,
or an instrument’s ring-out that is overly persistent. In these cases the threshold
is set somewhat higher, well up into the desired audio levels - in this way the
attenuation becomes part of the overall sound, but the gentle ratio prevents a
sense of anything “odd” happening. Again, relatively shallow depths of 12dB or
so are plenty to achieve the desired effect.
More aggressive expansion, or “gating”, is accomplished with steep ratios
(1:3, 1:5) and with shorter open and close times than for “unobtrusive”. It is still
best not to go overboard with depth - even just 14dB, 20dB tops, is enough to
make a signal “disappear” in the context of a mix; the whole gating sound,
especially surprisingly its opening, is less obvious with shallower depth.
Sometimes the “Surprise!” element is required, though, for effect.